There are in existence numerous devices for machining working surfaces in workpieces, including grinding machines and honing machines. In many applications it is desirable to apply a tool to such surfaces to remove material from the surfaces until a particular contour or profile is reached, such as a cylindrical contour in the case of the honing of engine block cylinders.
Some machine tool devices include visual displays of instantaneous machine load, such as the display disclosed in U.S. Pat. No. 4,887,221 which is assigned to the assignee of the present application. The displayed load is the load on the machine tool motor and is typically displayed, in either analog or digital form, on a percentage scale ranging from zero to one hundred percent, where one hundred percent represents a recommended maximum load for the machine tool motor. Some displays have also included indicator means, such as a flashing light, for signaling when one end of a stroke movement has been reached. However, as described below, none of the aforementioned displays have provided sufficient information to allow machine tool operators to easily determine the contour or profile of a working surface as it is being machined.
The instantaneous load of the machine tool motor will vary as the profile of the working surface varies. For example, in honing operations, when honing tight spots, or axial bore regions having a smaller diameter than the rest of the bore, a honing tool encounters more resistance and therefore requires more power to work its way through the tight spot. Accordingly, when the honing tool is honing a smaller diameter region, the instantaneous load of the honing motor is higher than when the honing tool is honing at larger diameter regions of the bore. Thus, the displayed instantaneous load is higher when the honing tool is honing the smaller diameter bore regions. Similarly, in other types of machine tool operations, such as grinding operations, the machine tool load will vary with the profile of the working surface being machined.
When operating machine tool devices that include the aforementioned displays, machine operators must separately observe both the instantaneous load and the stroke position in order to determine where the profile of the working surface varies. The operators then compensate for such profile variations. In particular, in honing applications, the operator changes the location of the workpiece with respect to the honing tool by moving the workpiece along the stroke axis or by moving the honing tool along the stroke axis, causing more honing to take place in the smaller diameter regions of the bore. In some machines, the operator can also vary the stroke length. Further, the operator can pause or dwell the stroking action of the honing tool while the tool is in the smaller diameter regions so that more material is removed from those regions. Thus, the operator is able to control the honing operation in order to achieve the desired cylindrical bore profile.
Problems with this instantaneous type of load display and operator control exist. For example, the detailed observation required for the machine operator to separately observe both instantaneous load and stroke position can result in mistakes or variations in working surface profiles based on the varying levels of operator skill, experience, and attention. Further, many machine tool devices include only a single motor for powering both tool rotation and tool stroking. In these single motor devices, the power required to reverse the stroking direction of the tool may register as a high load point on the instantaneous load display and can be mistaken for a working surface profile variation. Accordingly, machine operators must learn to distinguish between high load readings caused by the changing stroke direction and those caused by variations in the profile of the working surface. Based on these difficulties, operators cannot easily adjust to operating new or different machine tool devices. Thus, the skill of the operator and the mount of operator attention and experience contribute substantially to the cost of machining workpieces and to the accuracy and uniformity of the parts produced.
Recently, the workplace environment has seen a trend towards multi-tasking. More and more often, each worker is required to learn and perform more than one job in a particular working environment in order to increase the overall efficiency of the workplace. The prior art machine tools described above do not facilitate this trend due to the difficulty involved in learning to operate the machine tools and the difficulty involved in achieving workpiece uniformity as between different machine operators.
Accordingly, it is desirable and advantageous to provide a machine tool which allows a machine operator to easily determine the profile of a working surface being machined. It also is desirable and advantageous to provide a machine tool which effectively reduces the probability of incorrect or varying working surface profiles.
A principal object of the present invention is to provide a machine tool display of the profile of a working surface as it is being machined.
Another object of the present invention is to reduce the time and cost associated with training machine tool operators.
Another object of the present invention is to provide a machine tool graphical display which represents the profile of a working surface as it is being machined.
Another object of the invention is to provide a machine tool having a stroking and rotating tool wherein tool rotation is powered by a spindle motor which is independent of tool stroking.
Another object of the present invention is to provide a machine tool graphical display which continuously displays stroke position on one axis and machine tool load on an axis perpendicular to the stroke position axis.
Another object of the present invention is to provide a machine tool graphical display which continuously displays tool position on a first axis as a function of machine tool load on a second axis perpendicular to the first axis, and a mirror image of the relationship about a third axis which is parallel to the first axis so that the working surface profile is displayed.